In the related art, as a bearing used for a high-speed rotating body, a radial bearing is known which is used in a state of being attached to a rotary shaft so as to encircle the shaft. As such a radial bearing, a radial foil bearing is well known, including a thin sheet-like top foil which forms a bearing surface, a back foil which elastically supports the top foil, and a cylindrical bearing housing which accommodates the top foil and the back foil. As the back foil of the radial foil bearing, a bump foil is mainly used in which a thin sheet is formed in a wave sheet shape.
In some foil bearings, for example, in order to improve the damping effect by friction between foils or to increase the rigidity of the top foil, an intermediate foil is inserted between the top foil and the back foil (refer to Patent Document 1).
In such a radial foil bearing, in general, in order to prevent the detachment of the top foil or the bump foil from the bearing housing, one end portion (toe portion) thereof is directly fixed to the bearing housing or is indirectly fixed thereto via a spacer, using spot welding. Additionally, in general, the intermediate foil is disposed on the entire circumference of the bearing housing similar to the top foil or to the bump foil, and one end portion thereof is also fixed to the bearing housing through welding.
In addition, in order to perform mechanical fixing instead of welding, a radial foil bearing is also known, having a structure in which an end portion of a top foil or of a back foil (bump foil) is bent through bending machining and in which the bent portion is engaged with an engagement groove formed in a bearing housing (refer to Patent Documents 2 to 4).